High efficiency process for degassing of hydrogen sulfide from liquid sulfur

Abstract

Processes and systems for degassing liquid sulfur may include mixing a gas, such as air, with a liquid sulfur mixture comprising sulfur, hydrogen sulfide, and hydrogen polysulfides to form a sulfur-gas mixture. The sulfur-gas mixture may then be transported to a separator, storage vessel or storage tank for separating the sulfur-gas mixture.

What is claimed: 
     
       1. A process for degassing liquid sulfur, the process comprising:
 mixing a gas with a liquid sulfur mixture comprising sulfur, hydrogen sulfide, and hydrogen polysulfides to form a sulfur-gas mixture; 
 transporting the sulfur-gas mixture to a separator, storage vessel or storage tank; 
 separating the sulfur-gas mixture at a pressure below a water condensation point to recover a degassed sulfur product and a vapor stream comprising hydrogen sulfide; 
 wherein mixing gas with the liquid sulfur mixture comprises:
 introducing the gas into a suction of a sulfur transfer pump used for transporting the liquid sulfur mixture to the separator, storage vessel or storage tank; 
 introducing the gas into a transfer line during transport of the liquid sulfur mixture to the separator, storage vessel or storage tank; or 
 a combination thereof. 
 
 
     
     
       2. The process of  claim 1 , wherein the gas comprises air, nitrogen, oxygen, oxygen enriched air, SO 2 , CO 2 , Claus reactor tail gas, SRU tail gas and tail gas treatment unit recycle gas or tail gas, or a mixture thereof. 
     
     
       3. The process of  claim 1  or  claim 2 , wherein the gas is air having a relative humidity of less than 10% measured at 25° F. 
     
     
       4. The process of  claim 1  or  claim 2 , further comprising mixing a liquid degasification catalyst with the liquid sulfur mixture. 
     
     
       5. The process of  claim 4 , wherein the liquid degasification catalyst comprises one or more of cyclohexylamine, morpholine, or urea. 
     
     
       6. The process of  claim 1  or  claim 2 , wherein the separating is conducted at a temperature in the range from about 250° F. to about 300° F. and a pressure of less than 40 psig. 
     
     
       7. The process of  claim 6 , wherein the separating is conducted at a temperature in the range from about 260° F. to about 290° F. and a pressure in the range from about 20 psig to about 35 psig. 
     
     
       8. The process of  claim 1  or  claim 2 , wherein an average residence time of the liquid sulfur mixture during the transporting and separating steps is in the range from about 0.5 minute to about 30 minutes. 
     
     
       9. The process of  claim 1  or  claim 2 , wherein the separating comprises:
 feeding the sulfur-air mixture to an upper portion of the separator, storage vessel or storage tank; and 
 feeding air to a lower portion of the separator, storage vessel or storage tank. 
 
     
     
       10. A process for degassing liquid sulfur, the process comprising:
 transporting, from a sulfur pit or vessel, a liquid sulfur mixture comprising sulfur, hydrogen sulfide, and hydrogen polysulfides via a sulfur transfer pump; 
 introducing gas into a suction of the sulfur transfer pump, the sulfur transfer pump mixing the gas and the liquid sulfur mixture to form a sulfur-gas mixture; 
 separating the sulfur-gas mixture to recover a degassed sulfur product and a vapor stream comprising hydrogen sulfide. 
 
     
     
       11. The process of  claim 10 , further comprising:
 transporting, from the sulfur pit or vessel to a separator, storage vessel or storage tank, the liquid sulfur mixture; 
 separating the sulfur-gas mixture in the separator, storage vessel or storage tank to recover the degassed sulfur product and the vapor stream comprising hydrogen sulfide; 
 wherein the gas comprises air, nitrogen, oxygen, oxygen enriched air, SO 2 , CO 2 , Claus reactor tail gas, SRU tail gas and tail gas treatment unit recycle gas or tail gas, or a mixture thereof. 
 
     
     
       12. The process of  claim 11 , further comprising introducing additional gas into the sulfur-gas mixture intermediate the sulfur transfer pump and the separator, storage vessel or storage tank, where the additional gas introduced may be the same or different than that introduced into the suction of the sulfur transfer pump. 
     
     
       13. The process of  claim 11  or  claim 12 , further comprising feeding additional gas to a lower portion of the separator, storage vessel or storage tank and countercurrently contacting the additional gas with the sulfur-air mixture fed to the separator, storage vessel or storage tank, where the additional gas introduced may be the same or different than that introduced into the suction of the sulfur transfer pump. 
     
     
       14. The process of  claim 11 , further comprising transferring the degassed sulfur product from the separator, storage vessel or storage tank to a downstream vessel without additional pumping. 
     
     
       15. The process of  claim 10 , further comprising feeding a liquid degasification catalyst to the sulfur pit. 
     
     
       16. A system for degassing liquid sulfur, the system comprising:
 a sulfur pit or vessel containing a liquid sulfur mixture comprising sulfur, hydrogen sulfide, and hydrogen polysulfides; 
 a separator, storage vessel or storage tank; 
 a sulfur transfer pump for transferring the liquid sulfur mixture from the sulfur pit to the separator, storage vessel or storage tank; 
 a feed line for introducing pressurized gas to the liquid sulfur during transfer from the sulfur pit or vessel to the separator, storage vessel or storage tank, wherein the pressurized gas comprises air, nitrogen, oxygen, oxygen enriched air, SO 2 , CO 2 , Claus reactor tail gas, SRU tail gas and tail gas treatment unit recycle gas or tail gas, or a mixture thereof; 
 a separator, storage vessel or storage tank vapor outlet for recovering a vapor product comprising hydrogen sulfide; and 
 a separator, storage vessel or storage tank liquid outlet for recovering a degassed liquid sulfur product. 
 
     
     
       17. The system of  claim 16 , wherein the feed line is configured to introduce the pressurized gas to a suction of the sulfur transfer pump. 
     
     
       18. The system of  claim 16  or  claim 17 , further comprising a feed line for feeding additional gas to a lower portion of the separator, storage vessel or storage tank. 
     
     
       19. The system of  claim 16  or  claim 17 , further comprising an exchanger for increasing or reducing a temperature of the liquid sulfur mixture intermediate the sulfur transfer pump and the separator, storage vessel or storage tank. 
     
     
       20. The system of  claim 16  or  claim 17 , further comprising a feed line for introducing a liquid degassing catalyst to the sulfur pit or vessel.